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DNS RNDC
Port 953 is primarily used by the Remote Name Daemon Control (RNDC), a command utility for controlling the BIND DNS server. It facilitates secure, authenticated communication between administrators and the DNS server, enabling remote management tasks such as reloading zone files and flushing caches. RNDC operates over both TCP and UDP, and by default listens on TCP port 953, providing administrators fine-grained control over DNS server operations..
Overview:
Port 953 is reserved by convention for RNDC, a control channel for BIND (Berkeley Internet Name Domain), the most widely used DNS server software. RNDC allows administrators to securely send administrative commands to the named daemon, facilitating seamless remote management.
Protocol Details:
While RNDC primarily utilizes TCP on port 953, it may also employ UDP for certain operations or during initial communication. The connection is typically authenticated and protected via shared secret keys using HMAC-MD5 or newer algorithms, as configured in the rndc.conf and named.conf files. Commands sent through RNDC include reloading zones, refreshing configurations, enabling or disabling query logging, and shutting down the BIND server.
Operational Context:
System administrators rely on RNDC to manage DNS servers without directly accessing the server console, thereby streamlining DNS administration. Because it can control critical DNS functions remotely, ensuring correct configuration of access controls and key management is vital to maintain DNS integrity and availability.